Help Physics Girl, Live Sky essays, Watch exoplanets dance

February 28, 2023 Issue #532

The edge-on disk galaxy NGC 5866. Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA); W. Keel (University of Alabama, Tuscaloosa)

Do gooding

Doing some good

If you enjoy people talking to you about science then you probably know Dianna Cowern, aka PhysicsGirl. She’s terrific; not only great and enthusiastic at explaining fun science but also just a nice, wonderful person. I’ve written about her several times (here, here, and here), and had the pleasure of meeting her IRL a few times. She’s all that.

But right now she’s not doing so well. She’s suffering devastating effects from Long COVID, including MECFS — chronic fatigue syndrome. This is truly awful; besides just being completely wiped out all the time she’s had trouble breathing and has had to go to the ER twice.

She could use all our support. Head over to her Instagram and leave a comment if you can, or even better support her on Patreon. Even watching her videos on YouTube would be nice.

Dianna, me, and Simone Giertz in better times at San Diego Comic Con in 2018. This is my favorite photo of her. Credit: Phil Plait

Thanks.

Shameless Self-Promotion

Where I’ll be doing things you can watch and listen to or read about

I’m quite pleased to let y’all know that I am now writing vaguely regular* astronomy essays for Sky Safari, my favorite planetarium app, so I’m extra pleased to be writing for them.

The essays will usually be short, around 500 – 600 words, covering a single topic. The first one is live, called “The Colors of a Comet”, about why the recent comet C/2022 E3 (ZTF) was blue, green, and red.

Note: My essays are part of the Featured Stories, available to premium subscription members (which you can access through the SkySafari app or at LiveSky.com), so if you’re interested in observing the sky, sign up!

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* By “vaguely regular” I mean it’ll be twice a month but not necessarily on a fixed schedule. If you subscribe to LiveSky or have a premium subscription to Sky Safari you’ll see it pop up when a new one goes live.

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CORRECTION: I originally wrote that the articles were for Live Sky, but they’re actually for Sky Safari, and Live Sky is a feature of Sky Safari. My mistake, and my apologies for any confusion. Bottom line: Get Sky Safari with a premium subscription to read the articles!

Pic o’ the Letter

A cool or lovely or mind-bending astronomical image/video with a description so you can grok it

HR 8799 is a star located about 130 light-years from the Sun. It’s somewhat bigger and more luminous than the Sun, and at that distance is just barely visible to the naked eye in the constellation Pegasus.

It’s young, only about 30 - 40 million years old, and in 2008 astronomers discovered three massive planets orbiting it. A fourth was found a couple of years later.

The vast majority of all the 5,000+ exoplanets known at the moment were found via the transit method. But the planets around HR 8799 are part of a select few: They were discovered through direct imaging: Literally, images taken of the star revealed the presence of the planets. Only about 60 exoplanets have been discovered this way.

But it gets better. To be found this way the planets need to be far enough from their star not to be overwhelmed by its glare (even though astronomers employ a series of clever techniques to maximize the planet/star contrast in the images). That means they’re on wide orbits; the innermost one has an orbit 2.5 billion kilometers out from HR 8799, a little closer than Uranus is to the Sun. The most distant of the four is 10 billion kilometers out, more than twice the Sun-Neptune distance! That’s a long way.

And that means it takes them a long time to orbit HR 8799 — that’s called their period; think of them as “years”. The innermost planet takes over 40 years, and the outermost 4.6 centuries. Those are very long years.

But they do move.